1. Field of the Invention
The present invention relates to the field of mobile communication technologies. More particularly, the present invention relates to an apparatus and a method for supporting gateway node reselection in a communication system.
2. Description of the Related Art
FIG. 1 is a schematic diagram illustrating the structure of a Long Term Evolution (LTE) system in the prior art.
Referring to FIG. 1, a System Architecture Evolution (SAE) includes a User Equipment (UE) 101 which is a terminal device for receiving data. An Evolved-Universal Terrestrial Radio Access Network (E-UTRAN) 102 is a radio access network, which includes a macro base station (e.g., an evolved Node B (eNB)) providing the UE with an access radio network interface. A Mobile Management Entity (MME) 103 is responsible for managing mobile context, session context, and security information for the UE. A Service Gateway (SGW) 104 mainly provides the function of the user plane. In practical networks, the MME 103 and the SGW 104 may be located at the same physical entity. A Packet Data Network Gateway (PDN GW) 105 is responsible for the functions of charging, legal listening, and so on, which may be located at the same physical entity as the SGW 104. A Policy and Charging Rule Function (PCRF) 106 provides Quality of Service (QoS) policies and charging rules. A General Packet Radio Service Supporting Node (SGSN) 108 is a network node device providing routes for data transmission in a Universal Mobile Telecommunication System (UMTS). A Home Subscriber Server (HSS) 109 is a home subsystem of the UE, responsible for saving subscriber information including the current location of the UE, the address of the serving node, subscriber security information, packet data context of the UE, and so on.
With the increase in UE service data rate, operators provide a new technology of Selected IP Traffic Offload (SIPTO), in which in the process of the movement of a UE that has accessed a certain service, the network side can handover the UE automatically to a near radio network access point, which reduces the costs invested for the transmission network and provides a better experience for the high data rate. The current 3rd Generation Partnership Project (3GPP) standard has proposed that the network needs to support the abilities of SIPTO and Local IP Access (LIPA). In SIPTO, the UE accesses the Internet and other external networks through a Home evolved Node B (HeNB), a Home Node B (HNB), or an eNB. When the UE accesses the network, the network side selects a suitable user plane node for the UE. In LIPA, on the other hand, the UE accesses a home network and an intranet through an HeNB or an HNB. In the implementation of LIPA, the network side also needs to select a suitable user plane node for the UE. The user plane node may be a user plane network device or a user plane gateway. The suitable user plane node usually refers to a user plane network device or a user plane gateway near to the UE. For an SAE system, the user plane node is an SGW or a PDN GW. And for a UMTS system, the user plane node is an SGSN or a Gateway General Packet Radio Services (GPRS) Supporting Node (GGSN).
FIG. 2 is a schematic diagram illustrating an application scenario in which a network reselects a user plane node for a UE in order to allocate its resources in an optimized way in the prior art.
Referring to FIG. 2, when the UE changes position, when a UE handover to another base station, or when the operator updates the policies after the network has selected a suitable PDN GW or GGSN, it becomes possible that the network reselects another PDN GW or GGSN for the UE in order to allocate its resources in an optimized way. The current standards have not specified how to implement the process of reselection such that when the above situation occurs, the UE can not continue enjoying the data service normally, which impairs the user's experience.